powerpc/rtas: export rtas_error_rc() for reuse.

Also, #define descriptive names for common rtas return codes and use it
instead of numeric values.

Signed-off-by: Mahesh Salgaonkar <[e-mail]>
Signed-off-by: Michael Ellerman <[e-mail]>
Link: https://msgid.link/169235811556.193557.1023625262204809514.stgit@jupiter

arch/powerpc/include/asm/rtas.h

···
 #define RTAS_USER_REGION_SIZE (64 * 1024)
 
 /* RTAS return status codes */
+#define RTAS_HARDWARE_ERROR	-1    /* Hardware Error */
 #define RTAS_BUSY		-2    /* RTAS Busy */
+#define RTAS_INVALID_PARAMETER	-3    /* Invalid indicator/domain/sensor etc. */
 #define RTAS_EXTENDED_DELAY_MIN	9900
 #define RTAS_EXTENDED_DELAY_MAX	9905
 
···
 extern int rtas_set_indicator_fast(int indicator, int index, int new_value);
 extern void rtas_progress(char *s, unsigned short hex);
 int rtas_ibm_suspend_me(int *fw_status);
+int rtas_error_rc(int rtas_rc);
 
 struct rtc_time;
 extern time64_t rtas_get_boot_time(void);

arch/powerpc/kernel/rtas.c

···
 }
 EXPORT_SYMBOL_GPL(rtas_busy_delay);
 
-static int rtas_error_rc(int rtas_rc)
+int rtas_error_rc(int rtas_rc)
 {
 	int rc;
 
 	switch (rtas_rc) {
-		case -1: 		/* Hardware Error */
-			rc = -EIO;
-			break;
-		case -3:		/* Bad indicator/domain/etc */
-			rc = -EINVAL;
-			break;
-		case -9000:		/* Isolation error */
-			rc = -EFAULT;
-			break;
-		case -9001:		/* Outstanding TCE/PTE */
-			rc = -EEXIST;
-			break;
-		case -9002:		/* No usable slot */
-			rc = -ENODEV;
-			break;
-		default:
-			pr_err("%s: unexpected error %d\n", __func__, rtas_rc);
-			rc = -ERANGE;
-			break;
+	case RTAS_HARDWARE_ERROR:	/* Hardware Error */
+		rc = -EIO;
+		break;
+	case RTAS_INVALID_PARAMETER:	/* Bad indicator/domain/etc */
+		rc = -EINVAL;
+		break;
+	case -9000:			/* Isolation error */
+		rc = -EFAULT;
+		break;
+	case -9001:			/* Outstanding TCE/PTE */
+		rc = -EEXIST;
+		break;
+	case -9002:			/* No usable slot */
+		rc = -ENODEV;
+		break;
+	default:
+		pr_err("%s: unexpected error %d\n", __func__, rtas_rc);
+		rc = -ERANGE;
+		break;
 	}
 	return rc;
 }
+EXPORT_SYMBOL_GPL(rtas_error_rc);
 
 int rtas_get_power_level(int powerdomain, int *level)
 {